Field of the Invention
The present invention concerns a temperature-compensated pressure controller and an operationally reliable extinguisher as well as a process for filling a pressure controller according to the invention. Said pressure controller is intended to be utilized in fighting fires by being adapted to rapid discharge fire-fighting appliances.
On board, aircraft fire-fighting equipment is only ever used once and almost never throughout an entire fleet of planes. Therefore, there is statistically very little chance of the extinguisher ever being used. However, when it is required, this extinguisher should operate as well five or ten years after its manufacture as at its date of manufacture. Current methods for manufacturing extinguishers provoke risks of low rate leakage or bleeding which consequently render the appliances unserviceable or ineffective after being put into service for a certain period of time. In order to overcome this drawback, the prior art presents a solution that consists of permanently measuring the internal pressure of the extinguisher and in comparing it with a threshold pressure. Once the measurement drops below the limit pressure value, a microswitch mounted on a pressure pick-up supplies an alarm signal that is transmitted to the safety unit of the aircraft.
However, since the extinguisher is subjected to extremely variable temperatures, depending upon the site, time and altitude, the pressure prevailing inside the extinguisher also varies according to a complex thermodynamic law. Furthermore, these known extinguishers comprise two gaseous agents:
a propelling agent such as nitrogen; PA1 a fire-fighting agent such a halon.
However, these gases are generally miscible and account must be made for their eventual interactions.
The present invention offers a solution to these problems. It also provides increased simplicity of means, thereby rendering it less expensive to operate than conventional appliances. In fact, the present invention concerns a temperature-compensated pressure controller. The pressure controller comprises a first chamber, filled with a reference mixture having a thermodynamic characteristic similar to that of a mixture filling an enclosure to be controlled. It also concerns an extinguisher fitted with a safety device, comprising a propelling agent and an extinguishing agent in a gaseous form, characterized in that it comprises a sealed chamber filled with a mixture having a thermodynamic characteristic similar to that of the two agents in the extinguisher, a system measuring the differential pressure existing between the inside of the sealed chamber and the inside of the extinguisher per se and device actuated by the system for measuring the differential pressure and generating an alarm signal when the differential pressure exceeds a threshold value. The invention also concerns a process for filling pressure controllers according to the invention. The process consists in filling a tank with the reference mixture then in producing a primary vaccum upon the pressure controllers to be filled. The whole is introduced into a thermostat at a temperature higher than the critical temperature of the reference mixture. At equilibrium, the filling tank is connected to the pressure controllers to be filled. When equilibrium has been achieved, the pressure controllers are sealed and brough back to ambient temperature.